Waves
Textbook pages 92-99
Perception of Light & Sound
What is a WAVE?
A disturbance that travels through a medium
What is a WAVE?
A disturbance that travels through a medium Medium: a substance that carries the
disturbance from one location to another
What is a WAVE?
A disturbance that travels through a medium Medium: a substance that carries the
disturbance from one location to another▪ How? The particles of the medium interact
with particles next to them allowing the disturbance to travelExamples of a medium
Water Air Ground
What is a WAVE?
Transports energy from one place to another
What is a WAVE?
Transports energy from one place to another
What is a WAVE?
Transports energy from one place to another Particles of the medium are only
temporarily displaced from the rest position
What is a WAVE?
Transports energy from one place to another Particles of the medium are only
temporarily displaced from the rest position▪ Does not transport matter
Wave Characteristics
PropagationAmplitudeWavelengthFrequency
Propagation
Waves are distinguished by the way they propagate through a medium
Propagation
Transverse Waves Propagates perpendicular to the motion
of the mediumMOTION OF
THE MEDIUM
WAVE MOTION
Propagation
Transverse WavesCREST
TROUGH
Equilibrium
Propagation
Longitudinal Waves Propagates parallel to the motion of the
mediumWAVE MOTION
MOTION OF THE MEDIUM
Propagation
Longitudinal Waves Propagates parallel to the motion of the
mediumWAVE MOTION
MOTION OF THE MEDIUM
Propagation
Longitudinal Waves Propagates parallel to the motion of the
mediumWAVE MOTION
MOTION OF THE MEDIUM
Propagation
Longitudinal Waves Propagates parallel to the motion of the
mediumRegion of Compression
Region of Rarefaction
Amplitude (A)
Related to the amount of energy transferred by a wave
Amplitude (A)
Transverse Waves Maximum distance travelled by a
particle in the medium compared to its equilibrium position
Equilibrium
Amplitude (A)
Transverse Waves Depends on energy transmitted by the
waveENERGY AMPLITUDE
Amplitude (A)
Longitudinal Waves How tightly the medium is pushed together at
the compressions REGION OF LOW-DENSITY
COMPRESSION
REGION OF HIGH-DENSITY COMPRESSION
Amplitude (A)
Longitudinal Waves Depends on the density of compression
DENSITY AMPLITUDE
Wavelength ()
Length of a wave’s complete cycle Transverse Waves
Cycle
Wavelength () Length of a wave’s complete cycle
Longitudinal Waves
Cycle
Frequency (f)
Number of cycles per unit of time Measured in Hertz (Hz) – the number of
cycles per second 1 Hz = completes one full cycle in one second
Cycle Cycle
Speed at which a Wave TravelsSpeed of a wave depends on
Medium it travels in Temperature
Determine the speed at which a Wave TravelsSpeed = frequency x wavelength
Determine the speed at which a Wave TravelsSpeed = frequency x wavelength
v = f x v = speed (m/s) f = frequency (Hz) = wavelength (m)
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
G
R
A
S
P
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
G
R
A
S
P
f = 170.5Hz = 2.00m
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
G
R
A
S
P
f = 170.5Hz = 2.00m
v = ?
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
G
R
A
S
P
f = 170.5Hz = 2.00m
v = ?
v = f x
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
v = (170.5Hz)(2.00m)v = 341 m/s
G
R
A
S
P
f = 170.5Hz = 2.00m
v = ?
v = f x
Determine the speed at which a Wave Travels What is the speed of a sound wave
that has a wavelength of 2.00m and a frequency of 170.5Hz?
v = (170.5Hz)(2.00m)v = 341 m/s
G
R
A
S
P
f = 170.5Hz = 2.00m
v = ?
v = f x
The speed of the sound wave is 341 m/s
Types of Waves
Mechanical WavesElectromagnetic Waves
Mechanical Waves
Can only propagate in a medium
Mechanical Waves
Can only propagate in a medium
How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles
Mechanical Waves
Can only propagate in a medium
How? A disturbance changes the physical shape of the medium and passed onto neighbouring particles
Examples: water waves, sound waves, seismic waves
Electromagnetic Waves
Can propagate in a medium and a vacuum
Electromagnetic Waves
Can propagate in a medium and a vacuum Carry Radiant Energy
Electromagnetic Waves
Can propagate in a medium and a vacuum Carry Radiant Energy
Examples: light waves in space
Electromagnetic SpectrumCategories of electromagnetic
waves Classified by frequency and wavelength
FREQUENCY ENERGY
Electromagnetic Spectrum
Long
Low
Short
High
Electromagnetic SpectrumRadio Waves
Smallest frequency Invisible & transport little energy Example: Radio, Television, Microwaves,
Cellphones
Electromagnetic Spectrum Infrared
Invisible, but feel the warmth emitted Example: Night vision goggles, short-
distance communication (wireless keyboards, remote controls, etc.)
Electromagnetic SpectrumVisible Light
Only electromagnetic waves that can be seen by humans
Together, colours make up white light Example: Photography, movies,
computer screens
Electromagnetic SpectrumUltraviolet Rays (UV)
Invisible to humans Greater frequency, transport more
energy Responsible for suntans, but can cause
cancer Example: sterilization of surgical
instruments, treatments
Electromagnetic SpectrumX-Rays
High frequency Able to travel through media opaque in
visible light Example: baggage inspection,
radiography
Electromagnetic SpectrumGamma Rays
Highest frequency and transports the highest energy
Travel easily through matter Can cause burns, cancer, and genetic
mutations Example: cancer treatment, food
preservation
Homework
Read Textbook pages 92-99Do Workbook pages 49-52